Narrative:

Mcdu #2 would not come on line. Working with maintenance control we tried everything we could think of pwring the aircraft up several times. Contract maintenance was called and we were under way 2 hours late. As per the MEL; #1 could be inoperative but not #2; so maintenance swapped them leaving us with only 1 functional mcdu. I amended the release and pushed back. We were cruising at FL340 and I ACARS'ed dispatch with the delay code. When I tried to return to the radio page; it gave me a message on the scratch pad 'radio timeout;' locking me out of the radio page. That sector of ZZZ would only have me for another 25 NM and we were running out of time. I attempted to try to 'hard tune' the radios via both of the ccd's on the respective pfd with no success. I informed ATC of our situation and asked for vectors that would keep us in communication while we tried to figure a solution out with company. After exhausting all attempts; ZZZ said that we were left with no other choice than to declare an emergency; and offered me 4 airports to choose from to land. The only logical choice was ZZZ1 with gates and maintenance. WX was VMC; I briefed our flight attendants on our plan; explained everything to our passenger; and we (myself and my first officer) discussed any and all possible actions needed. I then informed ZZZ that we were ready for vectors and initiated our descent checklist to minimize any distrs as we came in range. Dispatch had already obtained a gate and ground crew was waiting. ZZZ approach and tower synchronized their frequency and we landed without further incident. Shortly after parking; maintenance arrived; reset the breaker. The gate agent completed the paper trail. We refueled and proceeded to ZZZ2.

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Original NASA ASRS Text

Title: DISPATCHED WITH ONLY A SINGLE MCDU ERJ-175 FLT CREW IS STYMIED WHEN IT BECOMES DYSFUNCTIONAL. MUST LAND AT A DIVERSION ARPT ACCOUNT UNABLE TO CHANGE COM FREQUENCIES.

Narrative: MCDU #2 WOULD NOT COME ON LINE. WORKING WITH MAINT CTL WE TRIED EVERYTHING WE COULD THINK OF PWRING THE ACFT UP SEVERAL TIMES. CONTRACT MAINT WAS CALLED AND WE WERE UNDER WAY 2 HRS LATE. AS PER THE MEL; #1 COULD BE INOP BUT NOT #2; SO MAINT SWAPPED THEM LEAVING US WITH ONLY 1 FUNCTIONAL MCDU. I AMENDED THE RELEASE AND PUSHED BACK. WE WERE CRUISING AT FL340 AND I ACARS'ED DISPATCH WITH THE DELAY CODE. WHEN I TRIED TO RETURN TO THE RADIO PAGE; IT GAVE ME A MESSAGE ON THE SCRATCH PAD 'RADIO TIMEOUT;' LOCKING ME OUT OF THE RADIO PAGE. THAT SECTOR OF ZZZ WOULD ONLY HAVE ME FOR ANOTHER 25 NM AND WE WERE RUNNING OUT OF TIME. I ATTEMPTED TO TRY TO 'HARD TUNE' THE RADIOS VIA BOTH OF THE CCD'S ON THE RESPECTIVE PFD WITH NO SUCCESS. I INFORMED ATC OF OUR SITUATION AND ASKED FOR VECTORS THAT WOULD KEEP US IN COM WHILE WE TRIED TO FIGURE A SOLUTION OUT WITH COMPANY. AFTER EXHAUSTING ALL ATTEMPTS; ZZZ SAID THAT WE WERE LEFT WITH NO OTHER CHOICE THAN TO DECLARE AN EMER; AND OFFERED ME 4 ARPTS TO CHOOSE FROM TO LAND. THE ONLY LOGICAL CHOICE WAS ZZZ1 WITH GATES AND MAINT. WX WAS VMC; I BRIEFED OUR FLT ATTENDANTS ON OUR PLAN; EXPLAINED EVERYTHING TO OUR PAX; AND WE (MYSELF AND MY FO) DISCUSSED ANY AND ALL POSSIBLE ACTIONS NEEDED. I THEN INFORMED ZZZ THAT WE WERE READY FOR VECTORS AND INITIATED OUR DSCNT CHKLIST TO MINIMIZE ANY DISTRS AS WE CAME IN RANGE. DISPATCH HAD ALREADY OBTAINED A GATE AND GND CREW WAS WAITING. ZZZ APCH AND TWR SYNCHRONIZED THEIR FREQ AND WE LANDED WITHOUT FURTHER INCIDENT. SHORTLY AFTER PARKING; MAINT ARRIVED; RESET THE BREAKER. THE GATE AGENT COMPLETED THE PAPER TRAIL. WE REFUELED AND PROCEEDED TO ZZZ2.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.